1. Field of the Invention
This invention relates to methods and apparatus for handling sheets or documents, and particularly to methods and apparatus for assembling or collecting form sheets in a set thereof.
2. Prior Art and Other Considerations
In certain types of sheet or document handling equipment form sheets are prepared on a web in a format of rows and columns before the sheets enter two juxtaposed receiving stations of collecting or assembling apparatus. As used herein, the term "form sheet(s)" includes any paper sheets which are adapted to be assembled or collected in a set thereof and which differ in any feature which can be detected by sensing or scanning. The columns of incoming sheets, which may be separated into parallel strips prior to entrance into the receiving stations, extend on the web substantially parallel to the longitudinal direction of incoming travel. Rows on the web comprise sheets prepared substantially side-by-side with respect to a direction transverse to the direction of incoming travel.
In the prior art it has been known to use juxtaposed receiving stations to receive juxtaposed incoming form sheets, to use transverse conveyance means disposed in one of the receiving stations, and to transfer the contents of one receiving station to the other receiving station. The transfer occurs in a direction which is transverse to the direction of incoming travel of the form sheets to the apparatus.
Such apparatus is known from U.S. Pat. No. 4,273,319, and forms a constituent part of an automatic serial mailing system wherein a sheet web (provided with marks) is cut by a cutter into individual form sheets; wherein the form sheets are then fed on parallel paths and then folded (if desired); and, wherein the form sheets are subsequently assembled in sets in accordance with previously detected marks on the sheet web. For this purpose, the transverse conveyor must be operated to transfer a form sheet from one sheet-feeding path to the other sheet-feeding path if, e.g., the sheet web has been marked by a computer output printer (having one or two printing units) in such a manner that the sheet form areas which belong to a set of sheet forms and are provided with the same code marks are disposed in sequence on the sheet web in a zigzag arrangement.
In the known apparatus, the receiving station provided with the transverse conveyance means contains a continuously revolving, endless belt conveyor having an upper course which lies in the plane of a sheet-supporting surface of the receiving station and occupies a substantial portion of that supporting surface. When a sheet, which may have been folded, if desired, has been delivered from one of the substantially parallel sheet-feeding paths to the receiving station provided with the transverse conveyor, that sheet is not immediately transferred in the transverse direction by the revolving belt conveyor to the other receiving station. An immediate transfer does not occur because the movement of the sheet is obstructed by retractable stops which protrude upwardly in the region between the receiving stations and which initially block the path of the sheet to be conveyed in the transverse direction. Only when control signals (generated by a controller in response to the code marks detected on the scanned sheet web) cause the stops to be retracted and cause sets of drop rollers to descend (so as to urge the form sheet which is to be transferred against the continuously revolving belt conveyor) will that form sheet be transferred toward the other receiving station in the transverse direction. That other receiving station is disposed on a slightly lower level so that it can be used to stack sets of form sheets up to a predetermined height, whereafter the entire set of form sheets is delivered by the last-mentioned receiving station to e.g., an enveloping line comprising a revolving enveloping chain.
In the known apparatus the sheet web comprising juxtaposed printed or written form sheet areas is longitudinally cut to separate adjacent form sheets. The separated form sheets must then be moved sufficiently apart to provide between the juxtaposed form sheets, which are fed on the sheet-feeding paths, a space which permits (1) the form sheets to be moved at least past stop means in the receiving station provided with the transverse conveyor, and which also permits (2) the form sheets to be placed without obstruction into the receiving stations which are spaced a predetermined distance apart. When the form sheets have been separated in the longitudinal direction, they must be moved laterally apart along a substantial length of the substantially parallel sheet-feeding paths because the sheet web and the individual form sheets exhibit a delicate response to a sudden change in the direction of travel on a short length of the feeding path. The fact that the form sheets (which have been separated in the longitudinal direction) must be laterally moved apart along a substantial length of the parallel sheet-feeding paths increases the space requirement of the entire system and reduces the handling rate.
Further difficulties sometimes occur in the known apparatus when paper has piled up in the receiving station provided with the transverse conveyor. In such instances access from above the receiving station must be permitted so that the cause of trouble can be eliminated. In the known apparatus, the pressure-applying means and the sets of rollers which cooperate with the continuously revolving belt conveyor involve a complicated structure which precludes easy access. Moreover, the bottom of the receiving station of the known apparatus is not easily accessible because the pressure-applying devices and sets of rollers, as well as U-shaped holding-down and guiding members, cannot be easily lifted.
In view of the foregoing, it is an object of the present invention to provide sheet collecting method and apparatus which increases the operating speed and efficiency of an automatic serial mail handling system in conjunction with which the sheet collecting apparatus operates.
An advantage of the present invention is the provision of compact sheet collecting apparatus which requires little space.
A further advantage of the present invention is the provision of sheet collecting apparatus which is easily accessible for repair and troubleshooting purposes.